Tag Archives: contrast

When I left off in the last post, Smartphone astrophotography part 2 – The Android app Camera FV-5, I had narrowed down all the big “camera settings” that could affect my attempts from 23 possibles to only 3 real ones to play with or test — contrast, saturation, and sharpness. When I read a bunch of articles online, such as at Astropix.com, the advice basically said:

Set Contrast to “normal” which I took to be medium (i.e. not low or high);

Set Saturation to “normal”, again being medium; and

Turn Sharpen off and fix in processing because while sharpening is nice, the potential benefit is balanced out by increasing the amount of noise.

Two of my other advisors basically said they never do anything with it in the iPhone app, and the other said he just leaves it medium / normal for all three.

However, since everyone tells me that you have to test it “on your equipment” to see what result you get, I set myself up to do a series of snaps…one with everything turned off, one with contrast at medium or high with everything else turned off, one with saturation at medium or high with everything else turned off, one with sharpness at medium or high with everything else turned off, one with all three at medium/normal, and one with all three at high.

Since I wanted to be able to “see” the difference I was getting, I set up on Jupiter and hoped for the best, while trying to set every other feature to automatic. Somewhat ironic, while I was still setting up, I managed to get a shot of Jupiter before I even got going that had faint bands. As an aside, I should also mention I was doing BRACKETED exposure compensation at the same time. I’ll talk about this in a subsequent post, but it basically is a way to do “BURST” mode while adjusting your exposure slightly. The meter goes from -2 to +2 in .5 increments…for those playing along at home, that means a total of 7 settings for exposure. The default is “0” in the middle. Bracketing allows you to do the standard default in the middle, but before it does, it takes some below (negative compensation) and above (positive compensation). I set it to do the full 3F (three shots) with 2 as the increment i.e. -2, 0, and +2. Basically -2 will dim it, 0 will be normal, and +2 would be brightened (potentially too much). The best one for Jupiter was for Auto with a -2 compensation.

Setup luck

It seemed like auspicious beginnings, I must confess, but those were at ISO100 and 1/30s. At the risk of spoilers, the next session didn’t live up to the opening. My opening base in full size looked like this (with contrast set to minimum, saturation set to minimum, and sharpness set to minimum). One of the sites recommended increasing ISO to about 1000 so you could see changes up and down, but it is more in the end about shades of bright white.

As I mentioned,I wanted to show a base of 0,0,0 (contrast, saturation, sharpness) against medium contrast and full contrast to see what impact the contrast setting would have.

Base

Medium Contrast

Full Contrast

There isn’t a whole lot of difference in the three other than as you increase the “contrast”, you actually don’t increase contrast “within” the image (i.e. within Jupiter), you just increase the contrast between Jupiter and the background. It basically makes the bright Jupiter go even brighter. And I thus lost the moons in the progressions. So contrast isn’t going to likely help me much, other than by needing to tone it down, not up.

For the saturation, I wanted the same test.

Base

Medium Saturation

Full Saturation

Now, saturation basically operated the way I expected. The more “saturated” the setting, the more Jupiter was whited out. So it’s not going to help much for already-bright objects, but may hinder somewhat.

For sharpness, same deal as the last two tests.

Base

Medium Sharpness

Full Sharpness

And yet, I’m not sure WHAT is going on in this one. The moons do seem a bit more pinpoint-like in the last one, but at the expense of definition around the edge of the planet.

End result? Not much difference no matter any of the settings, other than that it generally starts to whiten / overwhelm the image as I go much above the minimum. Admittedly, again, it was going to ISO1000 by default, which tends to overwhelm anyway, but even with the compensation at -2 for all of the above options, it wasn’t enough to make the images worthwhile.

I wasn’t quite done though. I wanted to do balanced settings.

Base

All three to medium

All three to full

As expected, any setting above “base” tends to just completely white out the entire shot. I tried one of the recommended combos and even the app’s default settings, but all of them overwhelmed the image. Even the last one tended to boost contrast high enough for me to lose the moons.

Base

Medium Contrast, Medium Saturation, Full Sharpness

App default: Medium Contrast, Medium Saturation, 3/4 Sharpness

I’d love to be able to say, “Hey, now let’s try this with ISO 100” and see what I get, but that wasn’t next on my checklist. In the end, I had three lessons learned:

A. Obviously, ISO1000 will almost always be too high for Jupiter (duh);

B. The contrast, saturation and sharpness can affect the brightness and whiting out of the image, regardless of their intent, and should likely be used exceedingly sparingly for solar system targets;

C. Sharpness had a bigger range, so if I was trying for a DSO where I needed more brightness, I might try shifting an extra 10% sharpness over whatever my saturation and contrast levels were, but for anything else, it’s probably better to just be at minimum.

Ultimately though, it’s easier to just turn all three to minimum and let the other settings control the image settings. Good to know they’re there though if I’m having other over exposure problems.